Who’s interested in a flexible PCB design and group buy, useable for either:
- a cost and time effective active 3 way (or 4 way) power amp, or
- a home theatre power amp, with say two (or more) channels bridged to drive a single sub.
Even entry level eg Marantz integrated home theatre receivers have pre-outs on all channels. It wouldn’t take much of an amp to better most built in power amps (or get similar or a little better quality to many HT dedicated power amps, for fewer $ even than second hand).
IMO it’s not worth spending too much on HT power amps. Better to put the money into speakers or other things.

The opamp based stereo power amps – the commercial Gaincard and Monarchy Audio SM-70; Linkwitz’s simple diy design based on the National Semiconductor LM3886, the “Gainclone” and variations, etc:
Better than eg many Rotel etc amps, certainly the Rotel home theatre power amp.
The Monarchy has been rated by some better than Aragon!

Simple, cheap, not "SOTA” but very good, especially for the cost and ease of construction.
Big attractions are:
- Depending on design, components total only 9-12!
- Dependent on components, *total* cost of a gainclone 2 channel power amp, is around $US 40-60.

The other day at Madisound Doug posted about the 8 amps needed to drive the active 3 way Linkwitz Orion.
To drive this, the mid and tweet each get an amplifier, and each of the two woofers get a channel– an 8 channel amp.
Other DIYers are doing other active 3 ways (I’m considering the Linkwitz Phoenix, and my own active 3 way).

Doug’s suggestion was combining 8 channels of power amplifier based on the LM3886, with SL’s Orion filters with the eight 3886s all onto ONE board.
SL doesn't think there would be much demand for a specific unified board.

(I’m not an amp designer, and not (just yet) an amp builder).
Some opamps (including the LM3886) are bridgeable.

There are newer opamps (eg the TDA 7293) that sound better.

Although the trigger for my idea was a post on Madisound, diyAudio seems to be the place for this. Need to agree:

(A) Number of channels (maybe 10 is better) and how much flexibility about what is bridgeable, to make either:
1. Stereo 3 way with more grunt in the bass,
2. For the more ambitious, a stereo 4 way
3. Stereo 3 way with dual subs (much the same)
4. 5 channel with all channels bridgeable
5. 6 channel with double power to the L/ R/ C and sub.
6. Etc

(B) The chip & design
Exact design, the power supply, how many power supplies, etc.
Multiple power supplies, maybe 4? 5? would be good.

(C ) Who to do the group buy - mailout. I would be prepared to do this.
I’m in Australia, so freight would be a little higher (though weight will be low).
Aksa boards are locally made, so this should be competitive. And eg for our US participants, the USD is worth about $A 1.70!

Isn't the idea behind the gainclone to do p2p wiring rather than PCB?? Also everyone interested in this group buy would need to decide on what spec, chips, topology, parts etc. to use.

I have just received my LM3875 samples from NS (Thanks NS - I will be paying for more NS parts on another project) and keen to get my gainclone going.

I'm looking for a home theatre amp with the following specs:
- As high as possible 2 channel quality
- 3 x surround sound using similar but lower quality parts to keep the costs down.
- Based on the Peter Daniels tweaked up recipe.

A group buy on the components as well as the PCB would be useful. I am also based in Australia and having a tough time sourcing components like Riken resistors, Alps pots & Black Gate caps without paying ridiculous prices in US$$$$. There is a group buy on Black Gate on this site's WIKI but it seems to be dead.

With a carefull layout and attention to detail, PCB may produce satifying results as well. I'm in a process of building my commercial GCs, which are p2p, but it is really time consuming task and when I imagine countless orders coming in, I don't know how I would manage with a demand.

__________________www.audiosector.com
“Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC

I never liked the idea of pcb for gainclones until recently. I realized that pcb's make it easier to connect both channels in the exactly the same way (length of connections) and ensure good connections. Also, the components can be mounted very rigid to the board. As long as the feedback resistor is soldered directly to the chip and the pcb is as SMALL as possible I do not see a problem. The original gaincard also uses a very small pcb and sounds great!

The man's a freakin* genius!
The man's a freakin* maniac!
The man's a freakin* glutton for punishment!
Ah what the hell, I'll take 10 channels. Out of small seeds may come the patter of little Krell feet.

This sounds like an interesting idea, Richard. Just wanted to remind you (and others) that Tim Harrison (trwh in here) has already done a small board for this range of IC's (link) which might be of interest.